The present invention relates generally to surface delay connectors for explosive blasting operations and is more particularly concerned with a new and improved millisecond delay surface connector unit that exhibits a wide flexibility of applications in blasting operations.
At present, surface delay connector devices used in blasting operations are almost exclusively of the bidirectional type since they eliminate the possibility of inadvertant hook-up in the wrong direction or the need for even considering the direction of propagation of the detonating impulse. These bidirectional delay connectors generally function properly when actuated from either end and are widely used to introduce appropriate time delay intervals between the initiation of selective explosive charges. Heretofore, such connectors have taken the form of relatively short shell-like metal tubes containing detonating charges on opposite ends with at least one time delay element between the explosive charges. The tubular connectors are generally open at both ends and are connected to a length of explosive cord, such as detonating fuse, through either a butt connection with the detonating charge or a lateral or side connection with the connector. The delay in detonation transmission is provided primarily by the delay element or portion thereof located adjacent the output end of the connector while the delay element or portion adjacent the input end of the connector is usually overridden or destroyed.
As will be appreciated, in a bidirectional connector it is necessary for the input end and the output end to have substantially the same characteristics in order to effect the bidirectional character of the delay unit. Accordingly, each end requires both sufficient sensitivity to pick up the explosive transmission signal and sufficient power to provide the requisite signal output. Additionally, such devices contain sufficient explosive material that, when closely packaged, they are subject to sympathetic detonation under impact or fire conditions. Further, since they are designed for use with detonating cord, they cannot be preassembled with the cord but must be spliced into a previously set out detonating cord trunkline that functions at a relatively high noise level.
Accordingly, it is an object of the present invention to provide a new and improved millisecond delay connector that is a reliable, safe and practical unit of far greater simplicity and versatility yet effectively provides the bidirectional delay connector function.
Another object of the present invention is to provide a delay connector of the type described wherein the explosive content of the assembly may be significantly lower than presently available commerical connectors. Included in this object is the provision for a device that will not sympathetically detonate due to fire or impact thus providing more favorable and economical shipping rates and added safety at the blasting site.
A further object of the present invention is to provide a surface delay connector capable of functioning as a replacement or substitute for a substantial portion of the detonating cord trunkline. Included in this object is the provision for a delay connector that not only operates as a trunkline at high velocity signal transmitting speed but which also achieves this function at a substantially lower noise level and in fact provides a trunkline function in essentially a noiseless manner.
A still further object of the present invention is to provide a connector of the type described which is capable of providing both the delay connector and trunkline functions and is also capable of functioning bidirectionally or in only a single direction without substantial modification to the unit.
Still another object and advantage of the present invention is to provide a millisecond delay connector unit which can be preassembled, packaged and shipped with the signal transmission tube in such a manner that both the connector and the tube are fully sealed from the atmosphere under controlled factory conditions. Included in this object is the provision for a connector that obviates the possibility of improper splicing into a detonating cord trunkline or inadvertent introduction of foreign matter that might totally or partially disrupt the time intervals between explosive charges in a blasting operation.
Other objects will be in part obvious and in part pointed out more in detail hereinafter.
These and related objects are accomplished in accordance with the present invention by providing a millisecond delay surface connector comprising a flexible explosive signal transmitting fuse of about one half foot in length or longer and a signal delaying and amplifying cap on each end thereof. The fuse includes an elongated hollow gas channel along its entire length and is adapted for sustaining a percussion wave at high velocity and low noise level. Each signal transmitting cap is secured to the fuse and housed within a protective block that also functions to provide secure interconnection with a length of detonating cord or similar signal transmitting element while at the same time providing a protective housing for the cap to substantially reduce sympathetic detonation between packaged multiples of similar assemblies.
A better understanding of the invention will be obtained from the following detailed description and the accompanying drawing of an illustrative application of the invention.